There is
also some want of propriety in the name of "Cincinnati Group,"
since the rocks which are known under this name in the vicinity of
Cincinnati itself are the representatives of the Trenton Limestone,
Utica Slates, and the old Hudson River group, inseparably united
in what used to be called the "Blue Limestone Series."].
Of the _life_ of the Lower Silurian period we have record in
a vast number of fossils, showing that the seas of this period
were abundantly furnished with living denizens. We have, however,
in the meanwhile, no knowledge of the land-surfaces of the period.
We have therefore no means of speculating as to the nature of
the terrestrial animals of this ancient age, nor is anything
known with certainty of any land-plants which may have existed.
The only relics of vegetation upon which a positive opinion can
be expressed belong to the obscure group of the "Fucoids," and
are supposed to be the remains of sea-weeds. Some of the fossils
usually placed under this head are probably not of a vegetable
nature at all, but others (fig. 36) appear to be unquestionable
plants. The true affinities of these, however, are extremely
dubious. All that can be said is, that remains which appear to
be certainly vegetable, and which are most probably due to marine
plants, have been recognised nearly at the base of the Lower
Silurian (Arenig), and that they are found throughout the series
whenever suitable conditions recur.
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